1) Interleukin-4 (IL-4) and its soluble receptor are being tested in the clinic for rheumatoid arthritis, asthma, and cancer by systemic injection or by gene transfer using viral vectors. Studies are underway to characterize structure, function, signal transduction and targeting of IL-4R expressed on immune and cancer cells. The structure and function of receptor for IL-13, another IL-4 related interleukin, is also being investigated. Reconstitution studies have demonstrated that IL-13R a' chain, but not a chain, is a novel component of IL-4R system. It is also demonstared that IL-4R b chain is a neccessary component of IL13R system. Thus, IL-4R and IL-13R share IL4Rb and IL-13Ra' chains. These studies help explain the similar biological activities of IL-4 and IL-13 on many different cell types including cancer cells. 2) To understand the molecular mechanism of signal transduction by the IL-4 and IL-13 receptor, we have studied the phosphorylation and activation of JAK kinases and signal transduction activator of transcription (STAT) intracellular proteins. Our studies demonstrate that both IL-4 and IL-13 can utilize similar tyrosine kinases, however, some differences do exist. IL-13 does not phosphorylate JAK3 tyrosine kinase. IL-4 can utilize either IL-13Ra' or IL-2Rg chain with IL-4Rb chain for its signal transduction. IL-13 also utilizes IL-4Rb and IL-13Ra' chain for signal transduction. These studies explain why IL-4 and IL-13 have redundant effects on a variety of cell types. Additional reconstitution experiments are underway to examine which kinases associate with various chains of IL-4 and IL-13R complexes. 3) The IL-4 and IL-13R directed targeting of a Pseudomonas exotoxin, Diphtheria toxin, or alternatively receptor directed gene transfer is also being investigated. The receptors for these two interleukins are expressed in abundance on human tumor cells that offer an attractive target for toxin therapy or gene therapy. In vivo experiments in nude mice using human brain tumor has demonstrated complete responses in 100% of the animals in response to circular permuted IL-4-toxin. Preclinical experiments including pharmacokinetics and toxicology in mice, intracerebral administration in rats and intrathecal and i.v. administrtaion in monkeys have been performed. Based on these results, our Phase I clinical trial was approved by CBER. We have treated eleven patients at John Wayne Cancer Institute, Santa Monica, CA with no evidence of toxicity. Additional patients are being enrolled at this site and seven additional sites are being added to this study. These clinical studies will help elucidate the potential safety and efficacy of this and other chimeric toxins being tested in clinic under various INDs.